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How to choose a cordless drill / screwdriver: expert advice

Choosing the right cordless drill or screwdriver can be overwhelming, especially for the uninitiated. However, with the right knowledge and guidance, the task can become much easier. This post provides expert advice allowing readers to learn about the features, advantages, and qualities that make the best cordless drill or screwdriver. You will learn about the size and torque of the tool, the battery and charger that comes with it, as well as the price range. With this knowledge, you can make a more informed decision and find the cordless drill or screwdriver that best suits your needs.

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It is difficult to imagine a technical installation in which a universal screwdriver would not be useful. Power tool stores are full of a variety of models, so we will learn to understand the assortment, get acquainted with the classification, device features and prices.

Drill-screwdriver: purpose and key differences

For people who are not particularly experienced in the range of power tools, it will be a big surprise to learn that there are several types of screwdrivers, and their classification is based on quite obvious signs. If we talk about cordless drills, the name itself can give at least three clues:

Rechargeable โ€“ it is suspected that the energy stored in the battery is the source of energy for rotating the spindle. This element is of key importance for the tool: its characteristics determine not only the battery life on one battery charge, but also the maximum torque and the ability to painlessly withstand peak loads.

How to choose a cordless drill / screwdriver: expert advice

Drill โ€“ means that the tool is capable of performing the drilling function. In practice, this is expressed in the installation of a three-jaw chuck on the leading edge of the spindle. The characteristics and quality of this unit determine the maximum size of the equipment for drilling and the durability of the entire tool as a whole. It is precisely by the presence of a chuck that the drill-screwdriver differs from wrenches and screwdrivers, which have only a six-sided bore hole.

A screwdriver means it is designed for screwing in screws, and at what it is of a completely different type. Technically, this function is expressed in the presence of an adjustable overload clutch that can be adjusted in accordance with the required tightening torque. Another distinctive feature is the ability to shift gears of the gearbox to increase either the speed or torque of the spindle.

How to choose a cordless drill / screwdriver: expert advice

However, even with such a categorical definition of a cordless drill-screwdriver, this tool can have a lot of differences in the design of the main and auxiliary units..

Battery type and capacity

As a rule, Li-Ion batteries are used in modern screwdrivers. This type of battery is characterized by a fairly long service life and almost complete absence of such disadvantages as memory effect and reduced energy efficiency at low temperatures..

However, there are also significant disadvantages. The maximum possible operating voltage of one Li-Ion battery is 3.7 V, while for normal operation of the engine, at least 12 V is required, and preferably at least 18 V. Because of this, there is an urgent need to use a bundle (battery) of 3 or 4 series-connected battery cells (or their parallel-connected groups).

How to choose a cordless drill / screwdriver: expert advice

It would seem, whatโ€™s wrong with that? The fact is that with this method of connection, a significant uneven charging is observed: it is enough for one battery to take a full charge, as the rest stop accepting energy. At the same time, the depth of discharge and the total capacity of the entire battery is determined by the least charged element of the chain, and these phenomena have a cumulative effect. Therefore, Li-Ion batteries require the use of a technically more advanced charger, which has so-called balancing contacts, which are connected to the intermediate nodes of the chain between the battery cells. The controller built into the charger determines the voltage on each battery group and, if necessary, adjusts the strength and voltage of the charging current so that all cells are fully charged.

How to choose a cordless drill / screwdriver: expert advice

Because of this, as well as due to the natural high cost of Li-Ion cells, the cost of batteries of this type for a power tool is higher than others, for example, based on nickel. Can I choose a different type of battery? Perhaps yes, but, firstly, the proliferation of nickel cells decreases from year to year due to the complexity of their disposal, besides, the additional costs for a Li-Ion battery fully pay off with high convenience and durability..

Engine and starting system

The main power unit of the cordless screwdriver is a direct current electric motor, it can have two designs. The most common is a permanent magnet brush motor, tools with it make up almost 90% of the entire range. The only plus of such an engine is the simplicity of the device, which explains the low cost of the tool. There are more disadvantages: relatively low efficiency, limited resource, almost zero maintainability.

How to choose a cordless drill / screwdriver: expert advice

In addition, brush motors can vary significantly in overall reliability. Thus, the presence of windows in the housing indicates air cooling, which reduces the risk of damage from overheating of the windings. The presence of a split casing (central sleeve and two flanges) may indicate the possibility of servicing bearings and replacing brushes.

Another type of electric motors are brushless, they serve as a kind of small-sized analogue of a full-fledged collector motor with a multiphase power supply. In this case, the motor itself has a not too complex device, but in general the drive unit is distinguished by increased technical perfection due to the presence of a driver โ€“ a microcircuit that regulates the power supply of the motor using the PWM method. Thanks to this, the engine runs quieter, has a higher efficiency, and its overall reliability is determined not by the electrical component itself, but by the quality factor of the body, the quality of processing of the bearing seats and, in fact, by the bearings themselves. The presence of cordless brushless tools is mainly found in professional and industrial tools such as Hilti or Mafel, but also found in professional models from Bosh, Hitachi and similar brands..

How to choose a cordless drill / screwdriver: expert advice

The brushless motor has another positive feature โ€“ a smoother control of the rotation speed. The electronic circuitry allows it to be carried out with high accuracy, while the combination for brush motors of a bipolar transistor and a potentiometer built into the button provides only relatively smooth starting without significant inrush current when energized. Long-term operation of such a starting system at low speeds is fraught with critical overheating and failure of the main elements, the button in this case requires a complete replacement.

The electrical part of cordless screwdrivers has two interesting options. The first โ€“ the reverse switch โ€“ serves as part of the design of the button and acts as a polarity switch. The second function provides DC braking on power failure. This is the calling card of all cordless screwdrivers: braking completely eliminates the inertial run of the spindle and greatly facilitates the control of screw tightening.

Varieties of gearboxes

The ability to change the modes of rotation of the screwdriver spindle is provided by a planetary gearbox. By itself, this assembly has an advanced design and is considered the most reliable part of the screwdriver, requiring no maintenance. However, there are some subtleties..

First you need to figure out the number of gear stages. In the simplest case, it can be only one, that is, the gearbox has an almost monoblock design with a motor and is designed to reduce the rotation speed to 400โ€“600 rpm with a proportional increase in torque on average to 20โ€“30 N / m. Single-stage gearboxes in cordless screwdrivers are very rare, as a rule, they are used in a power tool.

How to choose a cordless drill / screwdriver: expert advice

Two-stage gearboxes have an additional gear providing the spindle with a speed of up to 1000โ€“1500 rpm with a torque reduction of up to 10โ€“15 N / m. It is thanks to this option that the word โ€œdrillโ€ appears in the name of the tool โ€“ the second speed is intended exclusively for drilling. It can be assumed that the presence of a speed switch makes the design of the gearbox less reliable, but it was not for nothing that we mentioned that the transmission is planar, which means that when shifting, there is no change in the gear pairs. The increase in torque is carried out, as a rule, by blocking the carrier with the removal of rotation from the crown, which for the design of the gearbox is absolutely painless.

There is a third type of screwdrivers, the gearboxes of which have a third gear, which reduces the rotation speed to 150-200 rpm and increases the torque to the practical maximum. These screwdrivers are ideal for driving long dowels and threading. As in the previous case, the presence of the third gear does not imply a change in the pairs of engagement, it is just that the gears have a different ratio of gear ratios, and the gear with the highest speed is removed directly from the input shaft.

How to choose a cordless drill / screwdriver: expert advice

In general, the quality of a gearbox is determined by the reliability of its component parts. At the same time, the presence of plastic gears is not at all an indicator: if they are made of high-quality material (high-density caprolon, Zedex polyethylene, etc.) with a special coating, this is only a plus: the strength of the plastic is sufficient to withstand the existing loads, while the parasitic heating of rubbing surfaces and tool weight. The greatest load falls on the gearbox housing, so it is desirable that it be made of high-quality aluminum, duralumin or brass alloy. A detachable arrangement of body parts is also desirable for the possibility of changing the lubricant..

Coupling and chuck

The ability of a screwdriver to tighten screws and screws is due to a special unit that allows you to adjust the tightening torque of the fasteners. Structurally, this element is made in the form of a friction clutch with parabolic teeth and a set of metal balls, the pressing force of which to the clutch is regulated by the compression force of the spring.

How to choose a cordless drill / screwdriver: expert advice

Typically, screwdrivers can have up to 20-30 steps of the clutch switch. However, it is possible to use this regulator as a torque gauge only if the manufacturer in the operating manual provides a table of the relationship between the clutch positions and the actual torque limit. It should also be remembered that over time, the surfaces of the clutch wear out and the elastic properties of the spring decrease, which means that the accuracy of such adjustment may be distorted as the parts of the limiting clutch wear out. The durability of the clutch depends both on the quality of the material from which the clutch is made, and on the quality factor of the landing ring for rolling elements and their own hardness.

How to choose a cordless drill / screwdriver: expert advice

The chuck of most drills is a three-jaw keyless screwdriver. The high quality of this assembly is required only with frequent changes of the working tool and with significant loads on the spindle. In the cheapest models of screwdrivers, the chuck is considered a consumable item and is replaced as the jaws wear out. A quality tool is completed with higher class chucks with precision jaws. Chucks with a quick-release coupling are considered the most convenient, allowing you to remove the cam head and install a tool with a splined shank, which not only increases the speed of switching modes of operation, but also helps to reduce wear on the spindle seat under increased loads. In addition, we note that some drills have the function of locking the shaft, due to which the convenience of fixing tools with a round shank of a significant diameter in the chuck is increased..

How to choose a cordless drill / screwdriver: expert advice

Ergonomics and equipment features

If we consider the popular series of cordless drills, we can conclude that no cardinally innovative solutions have been invented for this tool over the past decade. In general, a standard and time-tested scheme is used, and all its elements are located strictly coaxially to exclude additional transition nodes from the design. With such a tendency towards constancy, the quality of a power tool is entirely determined by the reliability of its individual components, and therefore by the cost..

How to choose a cordless drill / screwdriver: expert advice

The pricing of screwdrivers can be determined not only by technical characteristics, but also by additional ergonomic features, which is also important. So, for professionals, it is of particular importance how comfortable the tool is in the hand and whether it can be easily removed from the holster when needed. The working process requires high mobility, and therefore such trifles as the shape of the handle, balancing (in the presence of a heavy battery), the supply of anti-slip pads and the dimensions of the screwdriver are very, very important. As an illustrative example, we can take the backlight function: if it is located in the area of โ€‹โ€‹the button, the shadow from the cartridge will fall directly into the work area. In reality, the backlight works correctly only when the light source is placed on the edge of the battery compartment..

How to choose a cordless drill / screwdriver: expert advice

Both professionals and DIYers should definitely remember the main disadvantage of choosing any cordless tool. The service life of even a very high-quality battery is limited to 4โ€“5 years, while batteries from the budget segment usually work normally only for 2โ€“2.5 years. And at the same time, there is no guarantee that the series of tools will not be discontinued and that it will be possible to select a battery of the appropriate type for a generally serviceable screwdriver. This issue is partly resolved in some series from leading manufacturers, in which batteries can be used to power not only a screwdriver, but also saber and circular saws, flashlights or other hand-held power tools..

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Comments: 5
  1. Serenity

    Can you suggest any specific features or qualities to look for when selecting a cordless drill / screwdriver? Are there any brands that are recommended by experts in this field?

    Reply
  2. Finley

    Can you provide some expert advice on how to choose the right cordless drill/screwdriver? Iโ€™m in the market for one but Iโ€™m not sure what features or specifications to consider. Any tips on what I should be looking for?

    Reply
  3. Juniper

    What are the key factors to consider when choosing between a cordless drill and a screwdriver? Are there specific features or specifications that an expert would recommend prioritizing?

    Reply
  4. Juniper

    What are the key factors I should consider while selecting a cordless drill/screwdriver?

    Reply
  5. Avery Kelly

    I appreciate the helpful information provided in this text about choosing a cordless drill/screwdriver. However, I would like to ask the experts for their advice on one particular aspect. When comparing different models, how important is the battery life? Are there other factors to consider that greatly impact the performance and versatility of a cordless drill/screwdriver? Thank you for your expertise!

    Reply
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